The present invention relates to radial pneumatic tires.
As materials improve, it has been the trend in the tire industry to reduce the gauges of tire components and the amount of material used to make a tire. The reduction in the amount of material in a tire reduces its weight, its rolling resistance, and makes the tire run cooler. It has been found, however, that the gauge in all portions of a tire cannot be reduced as much as the gauge in some portions of the tire and still produce a tire that has the durability and other properties of prior art tires with thicker gauges.
One of the ways in which the amount of material used in a tire can be reduced is to eliminate one or more of multiple components. For example, if a carcass ply can be made strong enough, two carcass plies can be replaced with a single carcass ply. Monoply tires can be used in applications where two carcass plies previously were needed.
It has been found that in radial pneumatic tires for highway driving, one area of weakness in a monoply tire is the shoulder area bridging the sidewall and crown of the tire.
It is known in the art to use a ribbon of ply rubber, about 0.020 inch (0.508 mm) gauge, in the shoulder/sidewall region of a high performance tire, and a similar ribbon having a higher gauge is used in light truck tires.
Until the present invention, no steel monoply carcass high performance tires ever passed durability tests. The inventors have discovered that the durability of a light weight tire is increased significantly by a gum rubber ply having a specific gauge, or by a fiber loaded reinforcement ply, strategically placed in the construction of a tire.
The present invention is a tire that employs a floating reinforcement ply bridging the intersection of a sidewall and crown area of the carcass. The tire of the invention is a pneumatic tire comprising a radial ply carcass, a tread disposed radially outwardly of the crown region of the carcass, and a belt assembly including at least one belt ply interposed between the tread portion and the crown region in circumferential surrounding relation to the carcass. The floating reinforcement ply is made from elastomeric material and in a preferred embodiment a fiber reinforced elastomeric material. Reinforcement fibers in a fiber reinforced ply are selected from the group consisting of polyamides, polyalkylenes, polyesters, cellulosics, inorganic fibers, aromatic polyamides and mixtures thereof.